Male sterile crops are industrially important in that they help avoid negative influences pollen dispersal has on the ecosystem, and facilitate plant crossings for selective breeding. Thus, it is hoped that plant gene recombination technology can solve food and environmental problems that are fast becoming modern-day issues. However, as many Japanese consumers are anxious about negative effects genetically modified crops may have on health and the ecosystem, the commercialization of these food products tends to be suppressed. Male sterility generating technology has important implications in solving these problems. In many crops, large numbers of male sterile strains are currently being selected and preserved as a genetic resource to facilitate crossing with other strains in selective breeding.
For this reason, there have been many attempts to produce male sterile crops. For example, a male sterile rapeseed produced by genetic recombination has already been commercialized. It has been reported that calcium- and calmodulin-dependent protein kinases are specifically expressed in the pollen-forming phase, and that recombinant plants with inhibited expression of these genes do not form pollen with normal germinability, causing male sterile plants (Takezawa, D. et al., U.S. Pat. No. 6,077,991, Jun. 20, 2000). In addition, a region that specifically regulates gene expression in pollen has been detected in the expression regulation region (promoter) of the proton translocating pyrophosphatase gene in the tonoplast membrane of Arabidopsis. Transformants in which gene expression is inhibited using this region are reported to become male sterile (Sato, Kyoto University, 2002).